Cellular and stromal edema are primary causes of decreased corneal transparency. This proposal is concerned with the physiology and biophysics of the corneal membranes in relation to their participation in the control of corneal hydration using the rabbit as an animal model. Transport and permeability properties will be studied with microelectrode techniques, radioactive tracer measurements, ion substitutions, pharmacological procedures, short-circuit current technique, ultrastructural techniques, thickness measurements, and computer simulation based on nonlinear irreversible thermodynamics. The mechanism of epithelial Cl transport will be studied in detail by determining the kinetics of the membrane "pump" and the role of paracellular pathways. A mathematical model for corneal hydration dynamics will be extended to include the effects of unstirred layers in cell cytoplasm and in bathing media. With this extension the phenomenological permeability coefficients of the corneal membranes will be determined for a variety of solutes. These data will be applied in the assessment of storage media and surgical methods designed to replace decompensated corneal epithelium and/or endothelium and/or endothelium with natural or artificial membranes. The influence of adrenergic innervation on epithelial transport will be studied. Neuroanatomical mapping procedures and combined neurophysiological and electrophysiological techniques will be used to assess the possiblity of neural control of epithelial transport in vivo.